Orifice plate flowmeter error and correction reasons

In the stage of use of the orifice flowmeter, the process piping needs to be purged several times, and the orifice flowmeter must be disassembled and disassembled frequently. If the orifice plate size is the same, an error will occur if it is not noticed. The exchange of the orifice flow meter will appear normal. The upstream and downstream surfaces of the orifice flowmeter are reversed. During the installation, the direction of the medium flow in the pipeline and the direction of the orifice flowmeter must be determined. Otherwise, the measured value will be low. This is because of carelessness. When mounting the orifice plate, the surface marked with “ + ” on the orifice plate flow meter should be on the upstream side of the flow direction. The main function of the pressure guiding pipeline is to transfer the differential pressure signal generated by the orifice flowmeter. The laying length of the pressure guiding tube should be between 3 and 20 meters. If the pressure guiding tube is too short, the flowmeter Flow measurement fluctuations will increase; if it is too long, measurement lag will occur.

In the industrial production process, most of the gas measurements are performed using standard orifice flowmeters and differential pressure transmitters, although the differential pressure transmitters can achieve a maximum accuracy of 0.075, but for various reasons. The measurement error is also very large, this problem will be more obvious when the differential pressure transmitter is used in industrial measurement. Therefore, it is of great significance to find the cause of the measurement error and the method to overcome. The orifice flowmeter is mainly composed of a pressure-conducting tube, an orifice plate, and a differential pressure transmitter. The throttling device element converts the flow of the medium into a differential pressure, and the differential pressure is transmitted to the positive and negative pressure chambers of the differential pressure transmitter membrane cassette through the pressure guiding pipeline. The isolation diaphragm of the positive and negative pressure chambers is passed through the silicone oil. The filling fluid transfers the differential pressure to the diaphragm that is measured, which can offset the measurement diaphragm from side to side.

The upstream and downstream surfaces of the orifice flowmeter may be damaged or the gasket of the orifice flange protrudes from the pipeline. In the process of transporting the orifice flowmeter or during the installation of the flowmeter by the constructor, the upstream and downstream surfaces may be damaged or The flange gasket protrudes from the pipe, which can cause the flowmeter to have a measurement error. The construction personnel should carefully inspect the orifice plate before installing the orifice flowmeter. If it is found that the upstream and downstream surfaces of the orifice plate are damaged, they should be promptly replaced. The design of the standard orifice flowmeter is obtained through a large number of experiments. It does not require actual calibration and can be used directly. Orifice flowmeters may have irregular or even wrong conditions during the installation process, resulting in flow. The measurement error is generated. Orifice flowmeters have unsatisfied straight pipe sections in front and in the back and forth. The front and rear straight pipe sections are used to ensure the stability of fluid flow in the pipe. However, due to the occurrence of bifurcations, bends, and other resistance components on the process pipe, fluid stability may occur. The phenomenon becomes disturbed, causing its measurement error. It can be used to design the installation position of the throttling device reasonably before and after the straight pipe section.

Feeds and Technical Support: Jiangsu Yuanchuang Instrument Co., Ltd.

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